Saber-toothed squirrel fossil found in Argentina

BUENOS AIRES, Argentina — Fossils of a tiny and previously unknown saber-toothed, squirrel-like creature have been discovered in Argentina, providing new clues to how small mammals lived among dinosaurs more than 93 million years ago, scientists said Thursday.

Cronopio dentiacutus had extremely long teeth, a narrow snout and large eye sockets, meaning it probably moved around at night to be able to survive among huge carnivorous beasts in the late Cretaceous period, according to the team that discovered the fossil in the Patagonian province of Rio Negro The fossil was found in a bed of sediment that also has produced a variety of much larger dinosaur bones.

The two partial skulls and jaws bridge a 60 million-year gap in the mammalian fossil record, said Sebastian Apesteguia, Leandro Gaetano and Guillermo Rougier, who described their find in Thursday’s edition of the journal Nature.

Christian de Muizon, a scientist at the Paris Museum of Natural History who was not involved in the find, called it “a major paleontological event,” considering that reasonably well-preserved fossils of the skulls of mammals from that period are so extremely rare. It’s the first mammal from the late Cretaceous period of the Mesozoic era ever found in South America, de Muizon said.

The little creature was probably less than 6 inches (15 cms) long and shared similar characteristics with the saber-toothed squirrel in the “Ice Age” movies. But Cronopio likely ate insects, not the nuts that drive the animated character “Scrat” so crazy, and was a dryolestoid, an extinct group more like today’s marsupials than squirrels, the scientists said.

“During the age of the dinosaurs, no mammal was bigger than a mouse, and they could do what they wanted, but under ground or at night — out of sight of the dinosaurs,” said Apesteguia, a researcher at Maimonides University in Buenos Aires.

“Such discoveries of remarkably complete Mesozoic fossils always represent giant steps” in mammalian paleontology, de Muizon added in a commentary in Nature. “In fact, one reasonably preserved Mesozoic mammalian skull in a critical stratigraphic and geographic position can be more relevant to our understanding of mammalian evolution and biogeography than hundreds of isolated teeth — even if teeth are the most common (and sometimes the only) remains” paleontologists work with.